Goals of this research project are to collect many mouse cDNA clones and prepare cDNA microarrays containing as many mouse genes as possible. The idea behind this work is to develop a method to monitor the expression levels of a large number of genes in various experimental conditions and to understand global changes of gene expression patterns in development and aging. The systematic analysis of expression patterns of a large number of genes quickly becomes the method of choice for many laboratories to understand biological systems. Accordingly the demand for high quality cDNA libraries and cDNA microarrays is increasing. In addition to 30,000 expressed sequence tags (ESTs) we generated in our previous work, we have generated 30,000 ESTs at NIA during this period. After scoring for redundancy, the 60,000 ESTs have been grouped into 15,275 sets of unique genes. This non-redundant gene set consists of 2132 genes from E7.5 extraembryonic tissue cDNA library, 893 genes from E7.5 embryonic tissue cDNA library, 7692 genes from preimplantation cDNA libraries (unfertilized eggs, fertilized eggs, 2-cell, 4-cell, 8-cell, 16-cell embryos and blastocysts), and 4620 genes. from E12.5 mesonephros and newborn ovary cDNA libraries. Sequence similarity searches against public sequence databases revealed that this gene set includes 3331 (22%) known (named) genes, 3526 (23.1%) new genes with some similarity to named genes, and 8418 (55.1%) new genes. Thus, this set of unique gene contains an unusually high fraction of novel genes. A set of these unique genes was rearrayed and the inserts of individual cDNA clones were amplified by PCR. The PCR products have been spotted onto a nylon membrane to make a cDNA microarray and have been used for differential gene expression analyses of the 15,275 component genes.Future plans include: the improvement of current methods to isolate full-length cDNA clones more efficiently, the expansion of the set of unique genes to 30,000 genes by sequencing more cDNA clones from various embryonic collections, and the preparation of cDNA microarrays from the expanded set of unique genes - Mouse development; cDNA project; EST project; cDNA microarrays